The present invention relates to a non-asbestos friction material used for the brake lining and clutch facing for cars and industrial machinery.
So far, as a basic material of friction material for the brake lining and clutch facing, asbestos useful as a heat-resistant reinforcing material has been used. However, from the pollution problem due to asbestos dust, friction materials without asbestos have become to be put into practice.
Here, from the studies on said dust, it is known that the problem of dust lies particularly in the shape thereof and that the thinner the diameter of needle-like shape of fibers used as reinforcing material, the more harmful.
After diligent studies to solve this problem, the inventors paid attention to the use of mica as a base material of friction material in the invention. As well known, however, mica is a stratified compound and has a low interlayer strength. Hence, when it is used for the friction material of brakes for cars running at high speed or industrial machinery heavily loaded, it became clear that mica caused interlayer splitting during braking to increase the wear.
There, as a result of further investigations, a non-asbestos friction material has been developed according to the invention, in which the interlayer splitting of mica is prevented and which is good in wear resistance and durable against high speed and heavy load.